Dr Muhammad Ibrar Ahmed

Transition metal carbides, known as MXenes, particularly Ti3C2Tx, have been extensively explored as promising materials for electrochemical reactions. However, transition metal carbonitride MXenes with high nitrogen content for electrochemical reactions are rarely reported. In this work, transition metal carbonitride MXenes incorporated with Pt-based electrocatalysts, ranging from single atoms to sub-nanometer dimensions, are explored for hydrogen evolution reaction (HER). The fabricated Pt clusters/MXene catalyst exhibits superior HER performance compared to the single-atom-incorporated MXene and commercial Pt/C catalyst in both acidic and alkaline electrolytes. The optimized sample shows low overpotentials of 28, 65, and 154¿mV at a current densities of 10, 100, and 500¿mA¿cm-2, a small Tafel slope of 29¿mV dec-1, a high mass activity of 1203¿mA mgPt-1 and an excellent turnover frequency of 6.1¿s-1 in the acidic electrolyte. Density functional theory calculations indicate that this high performance can be attributed to the enhanced active sites, increased surface functional groups, faster charge transfer dynamics, and stronger electronic interaction between Pt and MXene, resulting in optimized hydrogen absorption/desorption toward better HER. This work demonstrates that MXenes with a high content of nitrogen may be promising candidates for various catalytic reactions by incorporating single atoms or clusters. (Figure presented.).

Metal-free nitrides (MFNs) including carbon nitride (CN), boron nitride (BN), and borocarbonitride (BCN), have shown immense potential as single metal atom catalysts (SACs). They can act as excellent host support for anchoring and stabilizing single metal atoms. However, critical challenges related to the precise loading of single metal atoms and their accurate characterization are still being pursued. The current review explores the various aspects of MFNs-SACs. Synthesis methods including carbonization, self-assembly, microwave, ball milling and atomic layer deposition are discussed. Characterisation using X-ray absorption, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), Wavelet transform extended X-ray absorption fine structure (WT-EXAFS), and scanning transmission electron microscopy (STEM) which are useful to explore atomic-level structure and coordination of the MFNs-SACs are discussed in depth. The theoretical understanding of the structural framework of the MFNs-SACs using the packages including Vienna ab initio simulation (VASP), projector-augmented wave (PAW), Perdew-Burke Ernzerhof (PBE) and spin-polarized DFT is discussed in detail. A comprehensive discussion of electrocatalytic and photocatalytic applications of MFNs-SACs is evaluated. In the end, conclusions and future outlooks are provided with a focus on what is already achieved and what further can be achieved in the field by utilizing advanced scientific research and knowledge.

The electrochemical nitrogen reduction reaction holds great potential for ammonia production using electricity generated from renewable energy sources and is sustainable. The low solubility of nitrogen in aqueous media, poor kinetics, and intrinsic competition by the hydrogen evolution reaction result in meager ammonia production rates. Attributing measured ammonia as a valid product, not an impurity, is challenging despite rigorous analytical experimentation. In this regard, Li-mediated electrochemical nitrogen reduction is a proven method providing significant ammonia yields. Herein, fundamental advances and insights into the Li-mediated strategy are summarized, emphasizing the role of lithium, reaction parameters, cell designs, and mechanistic evaluation. Challenges and perspectives are presented to highlight the prospects of this strategy as a continuous, stable, and modular approach toward sustainable ammonia production.